ANNA David is on a roll. The hot brunette novelist — out this week with “Bought,” about a female journalist drawn into the world of Hollywood call girls — is already at work on her third book, “Sexual Healing,” which focuses on sexual addiction. “It’s about a guy who loses interest in women as soon as he has sex with them, until he meets the one woman who won’t sleep with him and becomes obsessed,” David told us at her book party at Frederick’s Downtown, adding it’ll be a steamy read — “filthy” — compared to the first two tomes.